Method and device for motor-braking by means of a multi-cylinder internal combustion engine

Abstract

Methods and apparatus for engine retardation in multi-cylinder combustion engines are disclosed including a hydraulic clearance regulator for regulating the clearance in a valve controller in response to a hydraulic fluid pressure below a predetermined maximum value in which the angular position of the crankshaft of the engine at which the exhaust valve in one of the engine cylinders is operated by an extra ridge on the camshaft is determined by the clearance in the valve controller. A pressure relief valve maintains the hydraulic fluid pressure below the predetermined maximum value, and a controller gradually reduces the clearance towards zero while the hydraulic fluid pressure in the valve controller is maintained below the predetermined maximum value so that the risk of operating the exhaust valve during a cylinder pressure greater than a predetermined elevated cylinder pressure is substantially reduced.

I claim: 
     
       1. A method for engine retardation in a multi-cylinder combustion engine including a crankshaft, a plurality of cylinders, a plurality of corresponding pistons for said plurality of cylinders, at least one exhaust valve for regulating the connection between at least one of said plurality of cylinders and an engine exhaust system, a valve control mechanism including at least one camshaft for continuously controlling said at least one exhaust valve in response to the position of said crankshaft, said at least one camshaft including at least one extra cam ridge, said method comprising selectively opening said at least one exhaust valve at least when at least one of said pistons corresponding to said at least one of said plurality of cylinders is in its compression phase by hydraulically controlling the clearance in said valve control mechanism in response to a hydraulic fluid pressure up to a maximum pressure value controlled by a pressure relief valve, whereby said at least one extra cam ridge causes said at least one exhaust valve to be opened at a predetermined clearance in said valve control mechanism, gradually reducing said clearance towards zero, and limiting the pressure in said hydraulic fluid controlling said clearance to a predetermined pressure value thereby reducing the risk of opening said at least one exhaust valve during a cylinder pressure greater than a predetermined cylinder pressure. 
     
     
       2. The method of claim 1 wherein said hydraulically controlling said clearance in said valve control mechanism comprises controlling the fluid pressure between a hydraulic fluid source connected to said valve control mechanism and said fluid pressure in said valve control mechanism. 
     
     
       3. The method of claim 2 wherein said engine include a plurality of valve control mechanisms, and including separately hydraulically controlling said clearance in each of said plurality of valve control mechanisms based upon the difference between said fluid pressure in said hydraulic fluid source and the fluid pressure in each of said valve control mechanisms. 
     
     
       4. The method claim 1 including maintaining direct communication between said hydraulic fluid source and said valve control mechanism when said fluid pressure is below a first predetermined value and when said fluid pressure is above a second predetermined value, said first predetermined value being less than said second predetermined value, and periodically closing said connection between said hydraulic fluid source and said valve control mechanism. 
     
     
       5. Apparatus for engine retardation in a multi-cylinder combustion engine comprising a crankshaft, a plurality of cylinders, a plurality of corresponding pistons for said plurality of cylinders, at least one exhaust valve for regulating the connection between at least one of said plurality of cylinders and an engine exhaust system, a valve control mechanism including at least one camshaft for continuously controlling said at least one exhaust valve in response to the position of said crankshaft, said at least one camshaft including at least one extra ridge, a hydraulically operated clearance regulator for regulating the clearance between said valve control mechanism in response to a hydraulic fluid pressure below a predetermined maximum value, whereby the angular position of said crankshaft at which said at least one exhaust valve is operated by said at least one extra ridge is determined by said clearance in said valve control mechanism, a pressure relief valve for maintaining said hydraulic fluid pressure below said predetermined maximum value, and control means for gradually reducing said clearance towards zero while said hydraulic fluid pressure is maintained below said predetermined maximum value whereby the risk of operating said at least one exhaust valve during a cylinder pressure greater than the predetermined value is substantially reduced. 
     
     
       6. The apparatus of claim 5 including a plurality of said valve control mechanisms for controlling a plurality of said exhaust valves, said hydraulically operated clearance regulator including a common hydraulic fluid source for said plurality of valve control mechanisms, hydraulic fluid duct means for connecting said common hydraulic fluid source with said plurality of valve control mechanisms, and a corresponding plurality of control valves in said hydraulic fluid duct means for sensing differences in the hydraulic fluid pressure between said valve control mechanisms and said hydraulic fluid duct means. 
     
     
       7. The apparatus of claim 6 wherein said plurality of control valves includes check valve means for opening said control valves at hydraulic fluid pressures in said hydraulic fluid duct means less than a first hydraulic fluid pressure value and greater than a second hydraulic fluid pressure value, said first hydraulic fluid pressure value being less than said second hydraulic fluid pressure value and for periodically closing said plurality of control valves.